SpaceX stated July 15 that the blast that destroyed a Crew Dragon spacecraft during a ground check in April was likely attributable to oxidizer that leaked into the spacecraft’s propulsion system and damaged a valve; however, didn’t give a firm schedule for continuing test flights.

The April 20 blast at Cape Canaveral occurred during testing of the thrusters on the same Crew Dragon spacecraft that flew the uncrewed Demo-1 program to the International Space Station in March. SpaceX was testing the thrusters, along with the smaller Draco thrusters as well as, the larger SuperDraco thrusters, ahead of an in-flight abort check of the spacecraft then planned for this summer.

SpaceX said all of the Draco thrusters were checked successfully; however, about a tenth of a second before the scheduled ignition of the SuperDraco thrusters, the accident took place that damaged the spacecraft. There were no officials within the range of the vehicle at the time of the test and thus no accidents.

SpaceX said the almost certainly cause of the explosion was when a “leaking part” let nitrogen tetroxide (NTO) oxidizer into helium tubes throughout processing. When the system was pressurized before the planned ignition, a “slug” of NTO was pushed at high velocity into a titanium test valve, resulting in a structural failure of the valve and igniting it, triggering the explosion.

While the investigation is going on — Koenigsmann stated the firm has worked through about 80% of the “fault tree” of possible reasons of the explosion — it was already taking steps to address this seemingly cause.